1,1-dicarbonyl substituted-1-ethylenes are of interest because they are capable of polymerizing at ambient temperatures with contact with basic materials. In addition their functional groups provide great flexibility in forming a variety of compounds and polymerizable compositions. 1,1-dicarbonyl substituted-1-ethylenes include methylene malonates. Such compounds have been known since 1886 where the formation of diethyl methylene malonate was first demonstrated by W. H. Perkin, Jr. (Perkin, Ber. 19, 1053 (1886)). The early methods for producing methylene malonates suffer significant deficiencies that preclude their use in obtaining commercially viable monomers, including unwanted polymerization of the monomers during synthesis (e.g., formation of polymers or oligomers or alternative complexes), formation of undesirable side products (e.g., ketals or other latent acid-forming species which impede rapid polymerization), degradation of the product, insufficient and/or low yields, and ineffective and/or poorly functioning monomer product (e.g., poor adhesive characteristics, stability, or other functional characteristics), among other problems. The overall poorer yield, quality, and chemical performance of the monomer products formed by prior methods have impinged on their practical use in the production of the above products. In recent years a number of commonly owned patent applications have been filed which have solved a number of the problems associated with the synthesis of methylene malonates and analogs thereof, for example U.S. Pat. No. 8,609,885 Synthesis of Methylene Malonates Substantially Free of Impurities; U.S. Pat. No. 8,888,051 Synthesis of Methylene Malonates Using Rapid Recovery in the Presence of a Heat Transfer Agent; and U.S. Pat. No. 9,108,914 Method to Obtain Methylene Malonate via Bis(Hydroxymethyl) Malonate Pathway. The synthesis procedures provided therein result in improved yields of heretofore-elusive high quality methylene malonates and other polymerizable compositions.
These applications disclose processes that are capable of producing 1,1-dicarbonyl substituted-1-ethylenes including methylene malonates in high quality which are capable of being used in a variety of high value chemical compositions and formulations. The disclosed processed prepare 1,1-dicarbonyl substituted-1-ethylenes including methylene malonates which contain 6 percent by weight or greater of the starting materials, 1,1-dicarbonyl substituted-methanes including malonates. The starting materials and the desired products have boiling points very close to one another which requires complex and costly processes in terms of capital and operating costs to separate the starting materials from the desired products.
U.S. Pat. No. 9,108,914 discloses preparing methylene malonates in a two-step process wherein the first step comprises reacting a source of formaldehyde with a dialkyl malonate ester in the presence of a reaction catalyst to form a diol reaction product comprising the dialkyl bis(hydroxymethyl) malonate composition; and reacting a dialkyl bis(hydroxyl-methyl) malonate composition in the presence of a suitable catalyst to form a methylene malonate monomer and isolating the methylene malonate monomer. The disclosed catalysts are bases, such as calcium hydroxide exemplified, which need to be removed before the second step to avoid unwanted polymerization of the 1,1-dicarbonyl substituted-1-ethylenes and methylene malonates. Where the catalyst is contains a metal such as, calcium hydroxide, passing the reaction mixture formed through an ion exchange column is used to remove the metals. This step adds both capital costs and increased operating costs due to the need to regenerate the ion exchange resins in the columns.
Thus, what is needed is an improved process that can prepare 1,1-dicarbonyl substituted-1-ethylenes and methylene malonates in higher purity with less starting material in the product produced which allows recovery of high purity material with simpler separation steps to reduce operating and capital costs. What are needed are processes which reduce the operating costs and capital costs of the first step of the process.